Safety device for jaw crusher



v Ma 12,1970 BWTEZ v 3,511,444

I SAFETY DEVICE FOR dAw CRUSHER Filed Aug. 1, 1968 United States Patent O Claims ABSTRACT OF THE DISCLOSURE In combination with a jaw crusher, a safety device which permits movement of the normally stationary jaw of the jaw crusher upon the occurrence of an overload force thereon. The force on the stationary crusher jaw is applied through intermediate blocking members to the far end of a prestressed bolt, the near end of which is restrained from movement, to thereby place the bolt in tension. The bolt is provided with a weakened region which fractures in tension at a predetermined force on the stationary jaw, to thereby release the blocking members to permit movement of the stationary jaw.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a safety device for a jaw crusher or the like, and more particularly to a safety device which yields in tension when the force against the crusher jaw reaches a predetermined magnitude.

Description of the prior art Occasionally, noncrushable objects, such as tramp iron, are introduced into a jaw crusher and it is necessary to provide some means by which one of the jaws of the jaw crusher can yield to permit passage of the noncrushable object to prevent serious damage to the crusher.

It is known to provide safety devices such as safety toggles which are intended to fail at a predetermined overload force on one of the crusher jaws. Most of the safety toggle devices with which I am familiar are designed to fail in shear, being disposed across the pressure line of the safety toggle. However, most of the safety toggles which operate on the shear failure principle are unsatisfactory since shear responsive devices are subject to progressive failure and fail merely due to progressive shear, rather than failing when the intended overload force is reached.

U.S. Pat. No. 2,767,597 issued to John Narsted on Oct. 23, 1956, and entitled Safety Toggle, discloses a safety toggle for jaw crushers which is so constructed as to fail in tension. Tension failure is much more precisely predictable than shear failure and hence the safety toggle of the Narsted patent is an improvement over the shear type failure devices of the prior art. However, the device of the Narsted patent has the disadvantagethat lubrication is required between the toggle arms and the bearing points therefor.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improved safety device for use with jaw type crushers or the like, which releases the crusher jaw when a predetermined overload force thereon is reached.

It is another object of the invention to provide a safety release device for jaw type crushers or the like which is so constructed as to fail in tension rather than in shear, since the value of tension required to cause the safety device to function to release the crusher jaw can be predicted with a high degree of accuracy.

It is still a further object of the invention to provide 3,51 1,444 Patented May 12, 1970 a safety release device for use with jaw type crushers or the like which does not require lubrication.

In achievement of these objectives, there is provided in accordance with this invention in combination with a jaw crusher a safety device which permits movement of the normally stationary jaw of the jaw crusher upon the occurrence of an overload force thereon. The force on the stationary crusher jaw is applied through intermediate blocking members to the far end of a prestressed bolt, the near end of which is restrained from movement, to thereby place the bolt in tension. The bolt is provided with a weakened region which fractures in tension at a predetermined force on the stationary jaw, to thereby release the blocking members to permit movement of the stationary jaw.

Further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view, partially in section, of a jaw type crusher embodying the safety device of the invention;

FIG. 2 is an enlarged view in horizontal section taken along the line IIII of FIG. 1; and

FIG. 3 is an isometric view of the U-shaped member which receives the tension bolt of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and more particularly to FIG. 1, there is shown a crusher generally indicated at 10 provided with a framework 12 comprising at least a pair of spaced apart frame side walls 14 and a transverse frame member 16. A stationary jaw 18 is attached in fixed position to the transverse frame member 16 but is capable of pivoting with respect thereto to the left with respect to view in FIG. 1 when the safety device functions as will be hereinafter described.

A movable jaw generally indicated at 20 is hung from a horizontally disposed drive shaft 22. The drive shaft 22 has end portions 24 journaled in the opposite frame side walls 14, and a midportion 26 eccentric to end portions 24. The midportion 26 of drive shaft 22 is journaled in an upper portion 28 of the movable jaw 20. The drive shaft 22 is rotatably driven by means not shown. A flywheel is mounted on shaft 22. In fact, two flywheels may be used, one being mounted at each end of shaft 22. Wear plates 30, 32 may be mounted on jaws 18 and 20 in a manner according to U.S. Pat. No. 3,153,- 512, issued to Henry H. Polzin, on Oct. 20, 1964, entitled Iaw Crusher. The jaws 18 and 20 and wear plates 30 and 32, along with side walls 14 define a crushing chamber 34 having an inlet opening 36 on top and a discharge opening 38 at the bottom.

A pair of flexible link bars 37 are provided, with one external to each of the framework sides 14 into which the drive shaft 22 is journaled. The bars 37 are each a leaf spring disposed to flex in planes perpendicular to the drive shaft 22. A first end of each bar 37 is fixed to crossbars 39 that project through aligned openings in the framework side walls 14 and are fixed to a lower portion of the movable jaw 20. The other end of each link bar 37 is fixed to the framework at a location spaced away from the drive shaft in a direction toward the fixed jaw 18. The detailed construction and operation of link bars 37 and elements associated therewith is described in my copending U.S. patent application S.N. 672,605, filed Oct. 3, 1967 now Pat. No. 3,465,975, to which reference is hereby made.

Alternatively, instead of using the flexible link bars 37, a toggle device may be interposed between the back side of the movable crusher plate 20 and the stationary framework as is well known in the art, as shown, for example, by U.S. Pat. 2,609,154, issued to Rhea V. Baker, on Sept. 2, 1952, entitled Means for Reducing Bulging of Crusher Jaw Face Plates. As still another alternative to using the flexible link bars 37, spring connections may be provided between the moving jaw and the stationary framework, such as the coil spring connections shown in the following patents:

U.S. 2,921,750Marcello Picalarga, Jan.

Stonebreaking Machines;

U.S. 2,996,26lMarcello Picalarga, Aug. 15, 1961, Feed and Discharge Screen Structures for Crushing Apparatus;

U.S. 3,001,729Rbert D. Conway, Sept. 26, 1961,

Free Vibratory Crusher; and

U.S. 3,145,938Harold C. Pollitz, Aug. 25, 1964, Dual Jaw Crusher.

The stationary jaw generally indicated at 18 includes laterally spaced rib members 40 on the back or left-hand face thereof with respect to the view shown in FIG. 1.

A pair of members 42 each having a curved contact surface is rigidly secured, as by welding, in spaced aligned relation to each other to the lower end of the rear face of the stationary jaw 18 and is the means by which force is applied from the jaw 18 to the safety device which will be described hereinafter. The members 42 extend transversely of the lower end of the rear face of stationary jaw 18. A pair of members 44 is rigidly secured as by welding to the bottom edges of the ribs 40, extending in spaced aligned relation to each other transversely and rearwardly of the bottom edges of the plurality of ribs 40. The members 44 serve as supports for a plurality of spacing shims 46 (see FIG. 2) which permit adjustment of the spacing between the stationary jaw 18 and the movable jaw 20. The shims 46 are arranged in two packs indicated at 46' and 46". The shim packs 46' and 46" are respectively aligned with the legs 58 and 60 of the U-shaped member 56 to be described. The shims are provided with a slot intermediate their length to permit hooking of the shims over the shim support members 44. A pair of force transmitting block members '48 which in effect are spacers between shims 46 and members 42, are rigidly attached, as by welding to the respective innermost shims facing members 42. The members 48 are thus supported by shim support members 44.

As best seen in the view of FIG. 1, an upper and lower retainer member 52 and 54, respectively, extend in vertically spaced horizontal planes and are rigidly connected to the framework of the crusher adjacent the lower end thereof, rearwardly of stationary jaw 18 and to the left of shims 46 with respect to the view of FIG. 1. Members 52 and 54 are vertically spaced from each other by a distance sufiicient to receive therebetween a horizontally disposed U-shaped blocking member generally indicated at 56 comprising a pair of legs 58 and 60 connected by a cross portion 62. Cross portion 62 has an enlarged head portion 63. The legs 58 and 60 are spaced from each other to define a window or gap 64 therebetween. A passage extending parallel to the legs 58 and 60 is provided through the cross portion 62 of the U-shaped member 56 and a tension bolt generally indicated at 66 extends through the passage just described. Tension bolt 66 is provided with a head member 68 which is received in an outer or left-hand recess, with respect to FIG. 2, of head portion 63 of the U-shaped member. Tension bolt 66 is provided with a threaded portion on the right-hand or inner end thereof with respect to the view shown in FIG. 2, and this threaded end is threadedly engaged with a restraining member in the form of a block member or nut 70.

Block 70 is received in the window portion 64 of the U-shaped member 56. The right-hand face of the block,

with respect to the view of FIG. 2, does not extend beyond the righthand ends of the legs 58 and 60 of the U-shaped member 56. Block 70 is of sufficient vertical height to bear against the edges of the retaining members 52 and 54, as best seen in the view of FIG. 1, and is thus prevented from moving to the left with respect to FIGS. 1 and 2. Tension bolt 66 is provided with a weakened portion 72 whereby the tension bolt will fail at a predetermined value of tension placed thereon as will be described hereinafter.

To prevent fatigue failure of tension bolt 66 during the normal operation of the crusher, bolt 66 is prestressed to cause a tension in the bolt in excess of the tension which would be caused by normal crushing force in the crusher. This pretension can be applied, for example, by tightening bolt 66 and nut 70 relative to each other by a torque multiplier wrench. Another method which can be used to prestress the bolt 66 includes the following steps: (1) Snug up nut 70 to normal tightness on bolt 66; (2) Heat bolt 66 in situ, as by application of a gas flame thereto, to cause the bolt to expand. The bolt will then become loose; and (3) While the bolt is still hot and is loose, tighten nut 70 a predetermined number of turns to produce a proper pretension in the bolt after the bolt cools.

The crushing force applied to the stationary crusher jaw 40 is transmitted through the curved contact surface members 42 to the force transmitting blocks 48 which in turn bear against the right-hand face with respect to the view in the drawings, of the shin packs 46' and 46". The left-hand face of the shim packs 46', and 46" with respect to the view in the drawings, bear against the outer ends of the legs 58 and 60 of the U-shaped member 56. Hence, the force applied to the stationary jaw 18 is ultimately transmitted through the U-shaped member 56 to the head 68 of the tension bolt 66. Since tension bolt 66 is already pretensioned to a value in excess of the tension which would be caused in the bolt by normal operating conditions in the crusher, the normal operating forces of the crusher do not affect the tension bolt.

However, when a predetermined value of tension on bolt 66 is reached due to an excess load on the crusher, the tension bolt will fail at the weakened portion 72 thereof and will permit the U-shaped member 56 to move to the left with respect to the view in the drawing, thereby permitting the stationary jaw to move to the left and relieving the overload pressure on the crusher, thereby preventing the possibility of serious damage to the crusher or its mechanism.

After the overload condition has been relieved by the failure of the tension bolt and the consequent movement of the U-shaped member 56, a new tension bolt may then be placed in position and pretensioned as previously described, to restore the safety device to operative condition again.

It can be seen from the foregoing that there is provided in accordance with this invention a safety device for use with jaw crushers and the like, which permits a release of the stationary jaw under overload conditions by a member which fails in tension. Since tension failure can be definitely predicted, the safety device of the invention provides a means which can be relied upon to provide relief at a definitely predictable value of overload and which is not subject to premature failure as is often the case when shear type overload release devices are used.

Furthermore, the safety release device hereinbefore described is uncomplicated in construction and reliable in operation, and the tension bolt can be easily replaced and pretensioned after a safety release action has occured.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and, therefore, it is aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A crusher comprising a framework, a pair of jaws defining a crushing chamber within said framework, one of said jaws being fixed to said framework, the other of said jaws being mounted for movement relative to said one jaw, and a safety release permitting movement of said one jaw upon application of an overload force thereto comprising a blocking member for receiving force from said one jaw, said blocking member normally preventing movement of said one jaw, a tension member engaging said blocking member to normally prevent movement of said blocking member, said blocking member engaging said tension member to apply the force on said one jaw to said tension member, means restraining said tension member against movement, said tension member having a weakened portion whereby a predetermined tension force on said tension member causes fracture of said tension member to release said blocking member to permit movement of said one jaw.

2. A crusher as defined in claim 1 in which said blocking member is provided with a passage therethrough and said tension member extends through said passage, said blocking member engaging an end of said tension member to apply the force on said one jaw to said tension member, and said means restraining said tension member at the opposite end of said tension member.

3. A crusher as defined in claim 1 in which said tension member is a boltlike member.

4. A crusher as defined in claim 1 in which said blocking member is of generally U-shape, including two spaced leg portions and a cross portion connecting said leg portions, said cross portion being provided with a passage therethrough for receiving said tension member, said tension member extending through said passage, said blocking member engaging an end of said tension member to apply the force on said one jaw to said tension member, said means for restraining said tension member against movement including a restraining member received in the space between said leg portions, the ends of said leg portions opposite said cross portion being positioned to receive the force on said one jaw.

5. A crusher as defined in claim 1 in which said tension member is prestressed to cause a tension in said tension member which is in excess of the tension caused by normal crushing forces in the crusher, whereby to prevent fatigue failure of the tension member due to normal crushing forces.

References Cited UNITED STATES PATENTS 1,281,055 10/1918 Moyle 241-32 1,363,270 12/1920 Rennerfelt 24l32 LESTER M. SWINGLE, Primary Examiner M.G. RASKIN, Assistant Examiner 

